experiment with -Wimplicit-fallthrough

net/base/gzip_header.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/base/gzip_header.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "third_party/zlib/zlib.h"
@@ skipping 83 matching lines @@
         pos++;
         state_++;
         break;
       case IN_XLEN_BYTE_1:
         extra_length_ += *pos << 8;
         pos++;
         state_++;
         // We intentionally fall through, because if we have a
         // zero-length FEXTRA, we want to check to notice that we're
         // done reading the FEXTRA before we exit this loop...
-
+        FALLTHROUGH_INTENDED;
       case IN_FEXTRA: {
         // Grab the rest of the bytes in the extra field, or as many
         // of them as are actually present so far.
         const int num_extra_bytes = static_cast<const int>(std::min(
             static_cast<ptrdiff_t>(extra_length_),
             (end - pos)));
         pos += num_extra_bytes;
         extra_length_ -= num_extra_bytes;
         if ( extra_length_ == 0 ) {
           state_ = IN_FNAME;   // advance when we've seen extra_length_ bytes
@@ skipping 57 matching lines @@
 
   if ( (state_ > IN_HEADER_OS) && (flags_ == 0) ) {
     *header_end = reinterpret_cast<const char*>(pos);
     return COMPLETE_HEADER;
   } else {
     return INCOMPLETE_HEADER;
   }
 }
 
 }  // namespace net